Control systems, such as those used to control the environment within a building, generally include one or more sensors, an operational unit and a controller. The sensors detect a condition, such as temperature, pressure, humidity, air velocity, or an operational status of a device, such as on or off. The operational unit includes equipment, such as a heater, a chiller, a fan or a pump, capable of changing the detected condition. The controller receives a signal from the sensors and provides a control signal to the operational unit to control the associated equipment.
Commonly, the operational unit is controlled via a negative feedback loop to maintain the associated condition at a predefined setpoint or within a predetermined range. The controller determines a difference between the actual condition value as indicated by a sensor and the setpoint. In response the operational unit is controlled to reduce or eliminate the difference to obtain the desired setting for the condition.
Complex systems, such as building management systems, can generate substantial quantities of data that could easily overwhelm a person supervising or monitoring the system operation. The person needs to identify potential or actual operational problems in the system and respond to solve the problems in a timely manner. To do this, operational information must be displayed in a manner which is clearly understood and utilized by the monitoring personnel.
Graphic interfaces developed for displaying control information in facility management systems are illustrative of prior art methods and devices for displaying operational information in complex control systems. In the 1960's, process control and facility management systems used mimic panels located throughout a facility. These mimic panels consisted of dials, gauges, valves and switches mounted on large panels painted with electrical, plumbing, process or HVAC (heating, ventilation and air conditioning) duct diagrams. System operation was monitored by touring the plant and monitoring the individual panels.
In the early 1970's, these hard-wired panels were replaced with centrally located minicomputers and cathode ray tube displays. This allowed for a concentration of sensor data and thus savings in time for personnel who no longer had to walk around the plant or buildings, recording and checking system data panels. To present relationships between the data and the elements of the monitored system, projectors would display slides of the pictures which were formerly on the mimic panels. Thus, a single sensor, single indicator (SSSI) paradigm was maintained. The static signal which represented function or location was displayed on the slide with the assigned name while the name and the current value was on the CRT. The operator was expected to view the projector and the display to determine the relationship between the sensor's function or location and its value.
Color CRT displays were introduced in the late 1970's, but these merely replaced the slide projector with dynamic values overlaying the static picture. This made the display two levels deep: a static portion or background level, representing functional or locational references, and a dynamic portion or foreground level displaying the current sensor values. The dynamic portion of the display utilized color to indicate the status of the sensor (alarm or normal) or a switch state (on or off). Analog values were represented with a bar graph element which showed relative values with limits added so the operator could determine how closely a monitored condition was maintained to a desired setpoint.
However, in modern, complex control systems, the number of sensed and controlled parameters has continued to grow. Some complex systems may have 400,000 such parameters, and future systems will certainly have even more. Prior art display systems will not enable a process manager to effectively monitor large numbers of parameters. Moreover, prior art techniques are still tied to the location and function diagrams of the physical system. To move beyond these diagrams, and to allow the system to accommodate even greater levels of complexity, it is necessary to provide an abstract representation of the physical data.
An abstract representation of the data would allow the data and relationships among the data points to be more effectively presented. By observing visual attributes in an abstracted display, as well as patterns and changes in the display, an operator could monitor a greater amount of data. The operator could also determine relationships between operational parameters of individual components of the control system.